1. Field of the Invention
The present invention relates, in general, to optical disk players used for reproducing data recorded on optical disks and, more particularly, to an optical disk player capable of effectively protecting an optical pick-up objective lens from foreign substances, such as dust.
2. Description of the Prior Art
As well known to those skilled in the art, optical disks, such as laser disks (LD) or compact disks (CD), have a high density data recording capacity and are almost completely and effectively used for a lengthy period of time in comparison with conventional magnetic tapes or LP records.
In order to play such optical disks and thereby to reproduce recorded data, several types of optical disk players, such as laser disk players or compact disk players, have been used. Of the known optical disk players, the compact disk players (CD players) have been more effectively, preferably and widely used since the CD players are small-sized so as to be convenient to users while carrying the disk players.
The signal format for such optical disks has been typically set to a conventional CLV(constant linear velocity)-type format which has a constant linear velocity at the inside and outside circular tracts of the disk "D" as shown in FIG. 1. As shown in the drawing, the inside section of a typical optical disk "D" is divided into a chucking place "a" free from any recorded data and a data place "b" having information and data about the disk.
A known optical disk player, used for operating the disks "D" having such a signal format, is shown in FIG. 2.
The disk player generally comprises three parts: a pick-up base 1, a turntable 2 and a pick-up unit 3.
In the above disk player, the pick-up base 1 is for supporting a plurality of parts of the disk player, so that it has a flat configuration. Both a guide rail 1a and a guide shaft 4 are set on the base 1 in a way such that the rail 1a is spaced apart from and parallel to said shaft 4. The above guide shaft 4 is held by a supporter 1b.
The turntable 2 or a disk drive means is set on the top surface of the pick-up base 1 and is for seating an optical disk thereon. In such a case, the disk is moved to the turntable 2 by a disk tray (not shown). The above turntable 2 is designed to be rotatable at a high speed by a spindle motor 5 arranged under the pick-up base 1.
The pick-up unit 3 is for reading the data recorded on the disk seated on the turntable 2. An objective lens 3a is set on the top wall of the pick-up unit 3 and is used for focusing a laser beam onto a desired portion of the optical disk.
The pick-up unit 3 is slidably held on the guide rail 1a at one sidewall thereof and slidably passes through the guide shaft 4 at the other sidewall. The above pick-up unit 3 is designed to be slidable in a radial direction relative to the disk while reproducing the data recorded on the disk. In such a case, the pick-up unit 3 is moved by the rotating force of a feeding motor 6, which is arranged under the pick-up base 1. The rotating force of the feeding motor 6 is transmitted to the pick-up unit 3 through a transmission gear train "G".
However, the above disk player is problematic in that the player may fail to stably or precisely read the data recorded on a disk. That is, the above optical disk player may undesirably cause an error while reading the recorded data of optical disks.
In the operation of the above disk player, an optical disk is moved from the outside to the inside of the player by a disk tray (not shown) prior to being seated on the turntable 2. However, foreign substances, such as dust, may be easily introduced into the interior of the disk player during such a disk feeding action of the tray. Such foreign substances may stick on the objective lens 3a of the pick-up unit 3, and cause the above-mentioned problem of data reading error.
That is, when foreign substances, such as dust, stick on the objective lens 3a of the pick-up unit 3, the lens 3a fails to appropriately focus a laser beam, emitted from a laser diode (not shown) of the pick-up unit 3, onto a desired point of the disk, but irregularly reflects the laser beam while reducing the optical efficiency of the pick-up unit 3 due to the foreign substances. This prevents the pick-up unit 3 from stably or effectively reproducing the data recorded on the disk.
In order to overcome the data reading error of the pick-up unit 3 due to the foreign substances, it is necessary to repeatedly clean the surface of the objective lens 3a. However, since the pick-up unit 3 is set in the housing of the optical disk player, it is very difficult for users to clean the surface of the objective lens 3a. Furthermore, some optical disk players are designed to completely prevent the users from gaining access to the objective lens 3a.
In an effort to overcome the above-mentioned problem, an optical disk player, which is designed to prevent foreign substances, such as dust, from undesirably sticking on the objective lens of the pick-up unit, is proposed as disclosed in Japanese Patent Laid-open Publication No. Heisei 6-274915.
The construction of the above Japanese optical disk player is shown in FIGS. 3 and 4 of the accompanying drawings. As shown in FIGS. 3 and 4, the Japanese optical disk player 10 comprises a pick-up base 10a, a pick-up unit 13 and a pick-up drive means. In the above disk player 10, the pick-up unit 13 is slidably held on the base 10a in a way such that the unit 13 is selectively slidable in a radial direction relative to an optical disk while focusing an optical beam onto a desired point of the disk and reproducing the data recorded on said disk. The pick-up drive means, comprising a feeding motor 14 and a transmission gear train 15, moves the pick-up unit 13 in a radial direction relative to the optical disk.
In the above optical disk player 10, a protection member 16 is provided on the pick-up unit 13 for selectively covering the objective lens 13a during a stop mode of the disk player. The above protection member 16 has an extension part 16a and is normally biased counterclockwise in the drawings by a spring 17.
In the operation of the above optical disk player 10, at a time the disk player 10 is stopped and returns the pick-up unit 13 to its waiting position by the pick-up drive means 14 and 15, the extension part 16a of the protection member 16 comes into contact with a fixed stopper 18 of the base 10a, thus rotating the protection member 16 clockwise in the drawings while overcoming the biasing force of the spring 17. Therefore, the protection member 16 covers the objective lens 13a of the pick-up unit 13.
It is thus possible for the protection member 16 to prevent foreign substances, such as dust, from sticking on the objective lens 13a.
In FIGS. 3 and 4, the reference numeral 6 denotes a contact switch which is selectively brought into contact with the pick-up unit 13 so as to selectively turn on or off the motor 14 of the pick-up drive means.
The above optical disk player 10 somewhat effectively prevents foreign substances, such as dust, from sticking on the objective lens 13a of the pick-up unit 13 due to the protection member 16. However, the optical disk player 10 has a serious problem in that an operational error is generated at a time the data reproduction mode of the player 10 is started, and so the pick-up unit 13 regrettably fails to reproduce the recorded data of the disk.
The above-mentioned problem will be described in detail with reference to FIGS. 1 and 5.
As shown in FIG. 5, when letting the distance between the center of the turntable and the waiting position of the pick-up unit 13 or the outside edge of the disk's chucking place "a" be "L" and letting the distance between the center of the turntable and the outside edge of the disk's data place "b" be "l", the difference between the two distances "L" and "l" is about 2 mm.
Therefore, the protection member 16 has to cover the objective lens 13a within an operational range of about 2 mm, and so it is necessary to make the protection member 16 be rotatable prior to covering the objective lens 13a while allowing the extension part 16a of said protection member 16 to come into linear contact with the stopper 18 with a gap between the extension part 16a and the stopper 18 being limited to a range of 0.5-1 mm. However, it is almost impossible for the protection member 16, designed to come into linear contact with the lens 13a as described above, to effectively cover the objective lens 13a having an outside diameter of about 6-7 mm.
In order to effectively open the objective lens 13a by the linear contact of the extension part 16a of said lens protection member 16 with the stopper 18, it is necessary for the protection member 16 to be positioned outside the objective lens 13a.
In other words, the protection member 16 only completely opens the objective lens 13a after the lens 13a has been already positioned within the data place "b" of the disk "D".
Since the data reproduction mode is started at a time the objective lens 13a has been positioned within the data place "b" of the disk "D" as described above, the pick-up unit 13 generates a data reproduction error. This makes the pick-up unit 13 regrettably fail to appropriately and precisely reproduce the recorded data of the disk.
The above protection member 16 thus completely prevents the optical disk player from performing an appropriate data reproduction mode, and so such a protection member 16 cannot be practically used in optical disk players.
Another problem experienced in the above Japanese disk player is that the linear contact between the extension part 16a of the protection member 16 and the stopper 18 results in an interference between the extension part 16a and the stopper 18. Due to the interference, the feeding motor 14 of the pick-up drive means is overloaded, and so the motor 14 may fail to perform a desired operation.